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Lightning Current

01/26/2017 8:05 AM

i just read the IEC standard on lightning protection as well as technical literature by pheonix contact,germany, where they say that 50% of lightning current flows up into system from earth termination system.any idea why? because from earth termination system ,all lightning current should be dispersed into soil and not travel back into system through earthing conductors.

Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain, and now disconnecting as Little England and Wales (not too sure about Wales bit, either). Kettle's on.

Re: lightning current

Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain, and now disconnecting as Little England and Wales (not too sure about Wales bit, either). Kettle's on.

Re: lightning current

01/26/2017 10:53 AM

Ground to cloud flow is due to ionization of air in between cloud and ground.same cannot be said about system.for current flow potential difference is required.and what is the purpose of using earth termination system if current is going upward in system .

Re: lightning current

01/26/2017 11:44 AM

Where do you want this current originating from? Anywhere on your building, or a "guided system" that allows flow from earth through your system and out the rod on top the building. Check out lightning characteristics of flow from cloud to ground or the other direction and you'll see that earth can be essentially a positive or negative source when it comes to lightning and that huge potential difference involved.

Re: Lightning Current

01/26/2017 10:34 AM

<Sigh>

Lightning is a static electricity effect. Thus a net positive or negative charge exists in the cloud prior to the strike. Half of the time (50%) it will be positive and the other half it will be negative.

Re: Lightning Current

01/26/2017 2:25 PM

Lighting travels to the path of least resistance. I do not know if you are going to introduced something, would actually make lightning to go down there as well. It might choose other way it certainly likes to discharge.

Re: Lightning Current

01/26/2017 3:12 PM

Lightning paths involve the suspended wind induced charged particles, water drops and droplets, dust particles. While most of the time these paths move faster than the eye can see they do move up, down, sideways all the time. It only takes a lucky but very fast camera to see this.

Re: Lightning Current

01/27/2017 12:46 AM

I will just place a self explanatory drawing here to explain my point. A total 10KA lightning current struck the arrester. 5KA (50%) dispersed in soil through earth termination mesh but a 5KA (50%) can flow upward into electrical system through circuit protective conductors. Surge protection devices (SPD) are installed on circuit protective conductors to prevent this back flow into electrical system.

Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain, and now disconnecting as Little England and Wales (not too sure about Wales bit, either). Kettle's on.

Re: Lightning Current

01/27/2017 4:57 AM

At those sorts of currents one might reasonably expect some capacitive and inductive coupling between the lightning rod down-comer conductor on the outside of the building and the conductors within the building.

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Re: Lightning Current

01/27/2017 5:26 AM

I don't think it is important how the lightning current will flow but more important how to protect buildings and installation against lightning. So, in my opinion, NFPA 780 it will be very interesting to study and not some theoretical presumptions.